1. Field of the Invention
The present invention relates to a recording medium that can achieve superior ink receptivity and blocking resistance even when ink is applied in a large quantity per unit area as in the case of forming a full-color image in a high density, and an image forming method making use of it.
The present invention further relates to a recording medium that can stably retain the above recording performance even after storage for a long period of time or at a high temperature and also has superior light-transmission properties, and an image forming method making use of it.
2. Related Background Art
Ink-jet recording has attracted notice as a recording process that makes less noise and enables high speed printing and multi-color printing.
Hitherto used as recording mediums in this ink-jet recording process are papers usually available, recording mediums called ink-jet recording papers, comprising a substrate and provided thereon a porous ink-receiving layer, and light-transmissive recording mediums used for OHPs (over-head projectors).
In recent years, with improved performance of ink-jet recording devices as in increasing high-speed and multi-color recording, properties of a higher grade and wider range have been increasingly required also with respect to the recording mediums.
In particular, it is necessary for the light-transmissive recording medium used in ink-jet recording to satisfy fundamental requirements that;
(1) the medium has excellent light-transmission properties; PA1 (2) the medium has excellent ink absorptivity; PA1 (3) dots are substantially round with smooth peripheries thereof; PA1 (4) the dots have a high OD (optical density), and are free from unclearness around the dots; PA1 (5) the medium has excellent blocking resistance; etc.
In particular, blocking may remarkably occur when a large quantity of ink is shot at one time onto the recording medium as in instances in which a recording head with a plurality of ink ejection openings (nozzles) is used and instances in which a full-color image is formed using inks of multiple colors. More specifically, the resin in the ink-receiving layer, having absorbed ink in a large quantity, is swelled and dissolved by the ink, which turns adhesive to cause the phenomenon that the resin adheres to the paper, plastic film or the like. This phenomenon is called a blocking phenomenon, and the property that may not cause the blocking even when a large quantity of ink is applied to the recording medium is called the blocking resistance.
Various studies have been hitherto made in order to satisfy the performance mentioned above, some of which have attained successful results to a certain degree. Under actual circumstances, however, no recording medium is known that has satisfied all of these required performances.
For example, U.S. Pat. No. 4,550,053 discloses a recording medium containing a condensation product of D-sorbitol with benzaldehyde. This condensation product is used in an amount of from 5 to 200 parts by weight based on 100 parts by weight of a polymeric material used in an ink-receiving layer.
In the materials used in the art as disclosed in the above publication, a recording medium in which the above condensation product comprises not less than 70 parts by weight based on 100 parts by weight of the polymeric material used in the ink-receiving layer can achieve a good blocking resistance.
However, storing this recording medium for a long period of time or at a high temperature brings about another problem that the above condensation product separates out of the ink-receiving layer to make it milky-white.
Ink-jet recording carried out on the above recording medium may also bring about additional problems of a low ink-absorption rate and a small initial dot size.
Namely, under actual circumstances, it has been difficult in the prior art to achieve both blocking resistance and storage stability.